Histological study on the effect of Ascocotyle (digenea: heterophyidae) infection on the heart morphology of the fish host. (South Carolina Academy of Sciences Abstracts).

Ascocotyle is a parasitic intestinal fluke of fish-eating birds and mammals. The juveniles exist as metacercarial cysts in various organs of the fish hosts. In the mummichog (Fundulus heteroclitus) the metacercariae are located in the bulbus arteriosus of the heart. A total of 40 mummichogs from three localities in the Massachusetts area and nine fish from Georgetown, South Carolina were examined for the presence of metacercariae. All fish from New Bedford Harbor were infected (mean intensity = 168; n = 25). Four out of five fish from West Island were infected (mean intensity = 2), and only one out often fish collected from Slocums River Basin was infected (intensity = 1). None of the fish from Georgetown were infected. All metacercariae were identified as those of Ascocotyle tenuicollis. Infection with these juvenile parasites produced no obvious signs of pathogenicity. To determine if morphological consequences resulted from metacercarial infection, histological sections of infected hearts were examined and compared with those of normal (uninfected) hearts. Extensive examination of the bulbus arteriosus and the ventricle revealed no significant damage to infected heart tissues. Examination of certain areas near the bulbo-ventricular junction, however, revealed areas of elongated nuclei and decreased width of muscle fibers, suggesting stretching of the cells. No evidence of tearing or any other damage was identified. Further examination of infected tissues with the electron microscope revealed similar. This research suggests that Ascocotyle infection has a minimal morphological effect on the mummichog heart.

Toni Hicks, Edna Steele
Department of Biology,
Converse College